1// Copyright (c) 2016, Google Inc.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15package runner
16
17import (
18	"encoding/binary"
19)
20
21// Use a different key from crypto/rand/deterministic.c.
22var deterministicRandKey = []byte("runner deterministic key 0123456")
23
24type deterministicRand struct {
25	numCalls uint64
26}
27
28func (d *deterministicRand) Read(buf []byte) (int, error) {
29	for i := range buf {
30		buf[i] = 0
31	}
32	var nonce [12]byte
33	binary.LittleEndian.PutUint64(nonce[:8], d.numCalls)
34	chaCha20(buf, buf, deterministicRandKey, nonce[:], 0)
35	d.numCalls++
36	return len(buf), nil
37}
38